Rainfall shapes the physiological condition, but not the body size, of an introduced dung beetle in Brazilian pastures

Abstract Seasonal rainfall patterns play a crucial role in shaping the biology, ecology and physiology of animals, particularly in tropical and subtropical ecosystems. Understanding these dynamics is critical under climate change scenarios, as shifts in rainfall regimes can disrupt phenological and physiological adaptations. However, physiological responses of Digitonthophagus gazella , an African dung beetle introduced worldwide for pasture improvement, to seasonal rainfall variation remain poorly understood. Here, we evaluated the effects of seasonal rainfall on body size, dry, lipid and muscle mass in D. gazella collected during the dry and rainy seasons in introduced Brazilian pastures. We sampled beetles in December 2023 (rainy) and July 2024 (dry), in two pasturelands sites ( Urochloa spp.) in Aquidauana, Mato Grosso do Sul. The sampling was carried out using light traps and directly from cattle faecal excrement in the pastures. Seasons did not affect D. gazella body size, dry and lipid masses. The dry season had individuals with higher muscle mass compared to the rainy season. These findings suggest that D. gazella individuals tolerate seasonal fluctuations, which may buffer them against seasonal environmental stress. Such plasticity may underlie the species' resilience and contribute to its successful establishment and ongoing expansion in tropical and subtropical pastures. Our findings highlight that rapid physiological adjustments can act as key mechanisms enabling D. gazella to withstand increasing climatic variability. Nonetheless, for a broader comprehension of seasonal effects on body condition of tropical dung beetles, more species and different ecosystems should be analysed in future studies.